Sleep fragmentation and arousals from sleep-time scales, associations, and implications.
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Arousal↗
Biomedical subjects
Robert Joseph Thomas
Publications and source records attributed to Robert Joseph Thomas.
Modafinil activates cortical and subcortical sites in the sleep-deprived state.
UNLABELLED: SUBJECT OBJECTIVES: To assess the effect of the wake-promoting drug modafinil on working memory and brain activation in the executive network, following a single night of sleep deprivation. DESIGN: Randomized, placebo-controlled, 4-arm, double-blind evaluation of a single 200-mg dose of modafinil on working memory (1-, 2-, and 3-back)-related functional brain activation and performance following overnight sleep deprivation. SETTING: General Clinical Research Center, Biomedical Imaging Center. SUBJECTS: Eight medication-free men, aged 21 to 35 years. INTERVENTIONS: Overnight sleep deprivation, single-dose 200-mg modafinil, functional magnetic resonance imaging MEASUREMENTS AND RESULTS: Brain activation patterns and regional signal intensity based on the blood-oxygen level-dependent signal were assessed. The following reaction times were used as measures of performance: (1) attention in the scanner before functional scanning, (2) "back" responses during the active-task block, and (3) attention during the baseline task block. Contrast of activation maps among conditions revealed sleep-deprivation and drug effects, and their interactions. Performance in the deprived state was enhanced by modafinil only at an intermediate (2-back) level of task difficulty and was associated with the recruitment of increased cortical activation volumes. Strong and consistent individual differences in performance were noted on the working memory tasks. CONCLUSIONS: Modafinil effectively counters the adverse effects of overnight sleep deprivation on working memory but only when task difficulty is moderate, recruiting extensive areas in the executive network to do so. Interindividual differences in working-memory performance are stable trait characteristics.
Adult↗
Effect of added dead space to positive airway pressure for treatment of complex sleep-disordered breathing.
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Continuous Positive Airway Pressure↗
Low-concentration carbon dioxide is an effective adjunct to positive airway pressure in the treatment of refractory mixed central and obstructive sleep-disordered breathing.
OBJECTIVES: To assess the efficacy of added carbon dioxide as adjunctive therapy to positive airway pressure-refractory mixed obstructive and central sleep-disordered breathing, using a prototype device-the positive airway pressure gas modulator. DESIGN: Open-label evaluation of low concentrations of carbon dioxide added to a positive airway pressure circuit. SETTING: Physician-attended polysomnographic titration in a free-standing sleep laboratory with end-tidal and transcutaneous carbon-dioxide monitoring. PATIENTS: Six adult men (age 54 +/- 5.7 years) with severe poorly controlled mixed sleep-disordered breathing in the absence of renal or heart failure. INTERVENTIONS: Flow-independent addition of incremental concentrations of carbon dioxide during sleep. MEASUREMENTS AND RESULTS: The respiratory disturbance index before treatment was 66 +/- 14.5 events per hour of sleep, with a nocturnal desaturation low of 84.6% +/- 10.1%. Residual respiratory disturbance index on best treatment was 43 +/- 9 events per hour of sleep. There was an immediate (<1 minute) response to the addition of 0.5% to 1% carbon dioxide, and minimal changes were required to be made across the night. There was no discomfort, shortness of breath, palpitations, headache, or significant increase in respiratory or heart rate. The residual respiratory disturbance index on carbon dioxide, scored irrespective of desaturations, was in the normal range (< 5 / hour of sleep). Two subjects had a second night at the concentration of carbon dioxide determined to be efficacious, with no required concentration change. No adverse effects on overall sleep architecture were noted. CONCLUSIONS: Low concentrations of carbon dioxide added to conventional positive airway pressure effectively control severe treatment-resistant mixed obstructive and central sleep-disordered breathing.
Blood Gas Monitoring, Transcutaneous↗
An electrocardiogram-based technique to assess cardiopulmonary coupling during sleep.
STUDY OBJECTIVES: To evaluate a new automated measure of cardiopulmonary coupling during sleep using a single-lead electrocardiographic signal. DESIGN: Using training and test datasets of 35 polysomnograms each, we assessed the correlations of an electrocardiogram-based measure of cardiopulmonary interactions with respect to standard sleep staging, as well as to the cyclic alternating pattern classification. The pattern of coupling in 15 healthy individuals was also assessed. SETTING: American Academy of Sleep Medicine Accredited Sleep Disorders Center. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: From a continuous, single-lead electrocardiogram, we extracted both the normal-to-normal sinus interbeat interval series and a corresponding electrocardiogram-derived respiration signal. Employing Fourier-based techniques, the product of the coherence and cross-power of these 2 simultaneous signals was used to generate a spectrographic representation of cardiopulmonary coupling dynamics during sleep. This technique shows that non-rapid eye movement sleep in adults demonstrates spontaneous abrupt transitions between high- and low-frequency cardiopulmonary coupling regimes, which have characteristic electroencephalogram, respiratory, and heart-rate variability signatures in both health and disease. Using the kappa statistic, agreement with standard sleep staging was poor (training set 62.7%, test set 43.9%) but higher with cyclic alternating pattern scoring (training set 74%, test set 77.3%). CONCLUSIONS: A sleep spectrogram derived from information in a single-lead electrocardiogram can be used to dynamically track cardiopulmonary interactions. The 2 distinct (bimodal) regimes demonstrate a closer relationship with visual cyclic alternating pattern and non-cyclic alternating pattern states than with standard sleep stages. This technique may provide a complementary approach to the conventional characterization of graded non-rapid eye movement sleep stages.
Electroencephalography↗
Arousals in sleep-disordered breathing: patterns and implications.
STUDY OBJECTIVE: To describe the whole spectrum of electroencephalographic (EEG) transients associated with the termination and recovery of obstructed respiratory events and, thus, widen the recognized spectrum of arousal phenomena from sleep. DESIGN: Retrospective review of diagnostic polysomnograms. SETTING: American Academy of Sleep Medicine (AASM)-accredited multidisciplinary sleep disorders center. PATIENTS: 17 patents with obstructive sleep-disordered breathing. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Nasal airflow using a nasal-cannula-pressure-transducer system and oral flow by a thermistor were used to score apneas and hypopneas; the latter included flow-limitation events. The EEG patterns that crested or occurred within 2 to 3 seconds of respiratory recovery were recorded, and posthoc categories were created for the purpose of tabulation ranging from an AASM 3-second arousal to a single K-complex with no electromyographic increase. Chi-square statistic was calculated to assess the difference in EEG patterns at event termination between apneas and hypopneas. Score-rescore agreement was tested. Apneas were significantly more likely to be associated with a 3-second arousal than were hypopneas, but all types of EEG change were seen with both types of events. Spindles were rarely seen with arousal-linked K-complexes. The majority of events in rapid eye movement sleep were terminated with visible electromyography tone increase. CONCLUSIONS: The spectrum of EEG change associated with the termination of respiratory events identified by using a nasal-cannula-pressure-transducer system is wider than that recognized as arousal phenomena by the 1992 AASM criteria. Scoring arousals with the 3-second rule may falsely minimize the apparent impact of abnormal breathing on sleep. The time may be right to update arousal recognition rules.
Arousal↗
Cyclic alternating pattern and positive airway pressure titration.
OBJECTIVE: To demonstrate that stability of the upper airway during continuous positive airway pressure (CPAP) titration is influenced by the microstructure of sleep as defined by the cyclic alternating pattern (CAP). METHODS: Retrospective review of 12 CPAP titration records. The patterns of flow-limitation during CPAP at subtherapeutic pressures were characterized as 'stable' (persistent and non-progressive inspiratory flow limitation) or 'unstable' (progressive increase in inspiratory flow-limitation terminating in an arousal), and continuous periods of at least 10 min were identified. Sleep stage scoring by both conventional Rechtshaffen and Kales criteria and the CAP were done. The relationship between flow type and CAP was determined. Responses to an increase in applied pressure on flow-limitation were noted. RESULTS: There were a total of 50 periods fulfilling the above criteria, totaling 1113 min of titration time. Thirty periods (757 min, 68% of total) showed a stable flow-limitation pattern. A total of 29/30 periods showing a stable flow pattern during sleep was scored as non-CAP, and only a single 18-min period of stable flow was scored as CAP. A total of 19/20 periods showing an unstable flow pattern was in sleep with CAP characteristics, the exception being a single 14-min period where unstable flow was noted in non-CAP. Flow-limitation was stable and non-progressive or absent during non-CAP, even at less than optimal pressures. This was noted irrespective of the presence or absence of delta sleep as scored by conventional criteria. Pressure increases during non-CAP, when the profile of the inspiratory flow was flattened, never resulted in a discernable change in the flow profile, while at least two-thirds of pressure increments during CAP periods improved flow. CONCLUSIONS: The microstructure of sleep as determined by CAP and non-CAP have practical implications for manual pressure titration algorithms and research on upper airway physiology during sleep. The appearance of a period of non-CAP, irrespective of conventionally scored delta sleep, may falsely suggest that the CPAP is optimal or close to it. Large increases in non-CAP that may be seen during a titration night can reduce the window of opportunity for titration. Increases in CPAP should be avoided in non-CAP.
Journal Article↗